Description of problem:
Backlight control doesn't work on the Samsung N145P netbook. Hitting the keys make the popup with the with the bar appear and it changes, but the actual brightness doesn't change. The problem seems to be the X server using the /sys/class/backlight/samsung/ interface that doesn't work instead of /sys/class/backlight/intel_backlight/ which works.
Booting with any of:
video.use_native_backlight=1
acpi_backlight=vendor
acpi_osi="!Windows 2012"
acpi_osi="!Windows 2009"
boot options doesn't help. What on the other hand helps is adding the following /etc/X11/xorg.conf.d/80-backlight.conf file:
Section "Device"
Identifier "Intel Graphics"
Driver "intel"
Option "AccelMethod" "sna"
Option "Backlight" "intel_backlight"
Driver "intel"
BusID "PCI:0:2:0"
EndSection
Version-Release number of selected component (if applicable):
xorg-x11-drv-intel-2.21.15-5.fc20.i686
kernel-3.15.0-0.rc3.git4.2.fc21.i686
How reproducible:
100 %
Steps to Reproduce:
1. try to change brightness level with special keyboard keys on the Samsung N145P netbook
Actual results:
no brightness changes
Expected results:
brightness changing

Hi,
(In reply to Paul Wolfger from comment #2)
> I have a samsung series 7 notebook (730U3E) using fedora 21 (uefi) and
> experience the same problem.
>
> Using ubuntu 14.04.01 backlight control works. Under ubuntu "ls -l
> /cat/sys/backlight":
> lrwxrwxrwx 1 root root 0 Dec 22 09:32 acpi_video0 ->
> ../../devices/pci0000:00/0000:00:01.0/0000:01:00.0/backlight/acpi_video0
> lrwxrwxrwx 1 root root 0 Dec 22 09:32 acpi_video1 ->
> ../../devices/pci0000:00/0000:00:02.0/backlight/acpi_video1
> lrwxrwxrwx 1 root root 0 Dec 22 09:32 intel_backlight ->
> ../../devices/pci0000:00/0000:00:02.0/drm/card0/card0-eDP-1/intel_backlight
>
> changing the brightness effects the values in acpi_video0 and not in
> intel_backlight
>
> in f21 I only have:
> lrwxrwxrwx. 1 root root 0 Dec 22 11:01 intel_backlight ->
> ../../devices/pci0000:00/0000:00:02.0/drm/card0/card0-eDP-1/intel_backlight/
> actual_brightness gets updated when using the fn keys, however the
> brightness does not change
Ok, this sounds like it has a different root-cause then the one of the original reporter, can you try booting with "video.use_native_backlight=0" added to your kernel commandline ? Then you should get back the acpi_video# entries under /sys/class/backlight, and hopefully that will also fix the backlight control.
Also please do:
sudo dmidecode > dmi.log
And attach dmi.log here. Please let me know if the kernel commandline parameter works for you, if it does then I'll add your laptop model to the kernel quirks table containing models which need "video.use_native_backlight=0" so that future kernels will do the right thing automatically.
Regards,
Hans

Thank you very much, this kernel parameter does the trick! I can now change the brightness by writing to /sys/class/backlight/acpi_video0/brightness.
However, using the fn keys or the slider in the gnome terminal does only change the values in /sys/class/backlight/intel_backlight/brightness. Do you know how to fix this behaviour?
The dmi.log is attached.
The exact model name:
# cat /sys/class/dmi/id/product_name
730U3E/740U3E
Best regards,
paul

Hi,
(In reply to Paul Wolfger from comment #5)
> Thank you very much, this kernel parameter does the trick! I can now change
> the brightness by writing to /sys/class/backlight/acpi_video0/brightness.
>
> However, using the fn keys or the slider in the gnome terminal does only
> change the values in /sys/class/backlight/intel_backlight/brightness. Do you
> know how to fix this behaviour?
That should not happen, have you perhaps but a custom xorg.conf file somewhere ?
If /sys/class/backlight/acpi_video0 is present then xorg (and via xorg gnome) should prefer it over intel_backlight.
Regards,
Hans

No I do not have a custom xorg.conf file. /etc/X11/xorg.conf.d contains a single file, which only defines the keyboard layout:
# cat 00-anaconda-keyboard.conf
#This file was generated by the Anaconda installer
Section "InputClass"
Identifier "anaconda-keyboard"
MatchIsKeyboard "on"
Option "XkbLayout" "at"
EndSection%
Best regards,
paul

(In reply to Paul Wolfger from comment #8)
> No I do not have a custom xorg.conf file. /etc/X11/xorg.conf.d contains a
Are you really really sure, have you also looked under /usr/share/X11/xorg.conf.d ? Your latest problem sounds a lot like you've a config file as described in comment 0 of this bug.
What desktop environment are you using ?

You were right, under /usr/share/X11/xorg.conf.d I had a config file. I'm sorry, I'm not familiar yet with these new locations.
Nevertheless, thank you very much for your help. Brightness control works now as expected!

Hi,
I've done a kernel scratch-build, with a fix for both the Samsung N145P and the Samsung series 7 issues discussed in this bug, please give it a try.
Please download the following rpms:
kernel-3.17.8-...rpm
kernel-core-3.17.8-...rpm
kernel-modules-3.17.8-...rpm
For your arch from here:
http://koji.fedoraproject.org/koji/taskinfo?taskID=8571559
(note this is still building atm)
Save them all to the same directory (which should not contain other rpms) and do:
sudo rpm -ivh kernel-*.rpm
From within that directory.
Then:
Vratislav: mv the custom xorg.conf file to somewhere where xorg will not find it; and
Paul: remove the "video.use_native_backlight=0" from the kernel commandline for the new kernel; and
Both: boot into the new kernel and check if the backlight works as expected.
Thanks & Regards,
Hans

(In reply to Vratislav Podzimek from comment #14)
> I can confirm that the kernel build from comment #13 works great on my N145P
> Samsung netbook. Backlight control works as expected out of the box, no
> special config nor boot option needed. Thanks!
Thanks, I've sent the patch upstream and asked Josh Boyer to add the patch fixing this to the official Fedora kernel builds for now.

Package kernel-3.18.2-200.fc21:
* should fix your issue,
* was pushed to the Fedora 21 testing repository,
* should be available at your local mirror within two days.
Update it with:
# su -c 'yum update --enablerepo=updates-testing kernel-3.18.2-200.fc21'
as soon as you are able to, then reboot.
Please go to the following url:
https://admin.fedoraproject.org/updates/FEDORA-2015-0724/kernel-3.18.2-200.fc21
then log in and leave karma (feedback).